Papers by Keyword: Hydrogen

Abstract: Sodium borohydride (NaBH₄) has several advantages as a hydrogen storage material compared to other hydrogen storage materials, such as metal hydrides, porous carbon, or other complex compounds. These advantages include a high storage capacity, the ability to release hydrogen under mild conditions, good chemical and thermal stability, and being non-toxic and environmentally friendly. These advantages make NaBH₄ the leading choice for hydrogen storage. In some of our previous investigations, we have studied the electrochemical release of hydrogen from NaBH₄, resulting in the formation of NaBO₂. The next problem is how to recover NaBO₂ to convert it back into NaBH₄. The method developed in this study is an electrochemical method with advantages in process control and scalability. This paper aims to convert NaBO₂ back into NaBH₄ electrochemically. The electrosynthesis of NaBH₄ from NaBO₂ was carried out in a two-chamber electrochemical cell separated by a bipolar membrane. The power supply controlled the current. The current used varied from 0.5 to 2 A. The concentration of NaBH₄ formed was analyzed using the iodate titration method. The formation of NaBH₄ occurs in the cathode chamber. The concentration of NaBH₄ increases with increasing electrolysis time. In general, the reaction rate of NaBH₄ formation increases at a current of 2 A. Meanwhile, the reaction rate of NaBH₄ formation at currents of 0.5 A and 1 A is almost the same. The greater the current used, the faster the NaBO₂ reduction process in the cathode chamber. The integral analysis method calculates the reaction order by integrating the reaction rate equation. The reaction orders tested are zero order, 1^st order, and 2^nd order. The best curve-matching results are shown in the second-order reaction rate equation. At a current of 2 A, the comparison curve between the data and the equation still indicates a relatively low fit. However, the second-order reaction rate equation gives the best results. The reaction rate constant is between 0.0406 and 0.0472 L mol^-1s^-1.

Abstract: Hydrogen represents a promising clean energy carrier with exceptional gravimetric energy density (120 MJ/kg) [1]. Metal hydrides offer superior hydrogen storage through chemical absorption at interstitial sites, enabling performance optimization via alloy composition [2,3]. However, Mg-based hydrides, despite their high capacity, exhibit limitations including strong Mg-H bonding and sluggish kinetics, necessitating elevated dehydrogenation temperatures (600-700 K) [4,5]. Molecular dynamics (MD) simulations provide detailed atomistic insights into mechanical behavior under hydrogenation conditions [6]. This investigation employs MD to elucidate the effects of hydrogenation on the mechanical properties of Mg-Pd-Ni ternary alloys, aiming to identify compositions with enhanced structural durability for practical hydrogen storage applications.

Abstract: Nowadays, the application of hydrogen as an energy carrier has become important as a result of decreasing availability of oil and gas fields as well as increasing demands on sustainable energy carriers. Providing an adequate hydrogen transportation infrastructure is a key step. During transportation, many different materials can interact with hydrogen, but in order to transport high quantities of hydrogen at higher pressures, the use of steels is preferred. However, hydrogen has many negative effects on steel, thus extensive research needs to be performed before hydrogen can be transported safely. Solubility of hydrogen in steel depends on the temperature, pressure, and the crystal structure of steel, so welding is also an important subject. Since most of the steel structures are welded, welded joints should also be examined for exposure to hydrogen. In the case of welding, a number of factors can decrease the hydrogen resistance of the welded joint and thus increase the risk of degradation by hydrogen. In this research work, hydrogen damage, and hydrogen traps will be reviewed. Possible ways to reduce the diffusible hydrogen content will also be summarized, as well as aspects of the filler material and shielding gas selection. In addition, an overview will be provided on welding technology aspects of carbon steels related to hydrogen, such as heat input, preheating, t_8/5 cooling time, heat-affected zone size, number of weld runs, effect of discontinuities, etc. In general, filler material with the lowest possible diffusible hydrogen content should be used; for electrode coatings and fluxes, special care should be taken to ensure proper baking; for wire electrodes, care should be taken to ensure surface cleanliness; in case of shielding gas the use of the purest possible shielding gas is recommended, and the use of shielding gas containing hydrogen is prohibited; and strict attention must also be paid to the purity of the base material. In addition, other important considerations for welding technology development will be outlined for carbon steels. Such as pipelines, where the most important technological aspects of welding will also be discussed, e.g. low heat input, multi-pass weld design, etc.

Abstract: The article analyzes the systems for generation, purification, transportation and storing of gaseous hydrogen as the alternative renewable energy source for ensuring of level of ecological safety of power plants with reciprocation internal combustion engines exploitation process. Purpose of the study is to improve the description of the process of purifying gaseous hydrogen from associated impurities during its production, storage and transportation based on the results of mathematical modeling analysis using improved mathematical apparatus based on modified thermodynamic perturbation theory. Problem of the study is the imperfection of the existing mathematical apparatus for describing the processes of purification of gaseous hydrogen as a commercial product and renewable ecological safe energy carrier using sorption metal hydride technologies based on TiMn_1,5. Idea of the study is to develop a list of recommendations and organizational and technical measures for obtaining ultra-high purity gaseous hydrogen in environmental protection technologies by improving the adequacy of the mathematical description of the processes of its sorption-desorption by intermetallic compounds based on TiMn_1,5. Task of the study is to adapt the mathematical apparatus of the modified thermodynamic perturbation theory to describe the process of selective sorption of hydrogen by metal hydrides of the type TiMn_1,5 from gas mixtures obtained during its production, storage and transportation. Object of the study is sorption processes in metal hydride technologies for the purification of gaseous hydrogen as an alternative fuel and a useful commercial product based on TiMn_1,5. Subject of the study is mathematical description of the course of hydrogen sorption processes by intermetallic compounds of the type TiMn_1,5 when purified from gas impurities. Methods of the study are literature analysis, modified thermodynamic perturbation theory, mathematical modeling. Scientific novelty of results of the study is for the first time, an apparatus for mathematically describing the processes of hydrogen sorption by intermetallic compounds of the type has been suggested TiMn_1,5 from gas mixtures during its production, storage and transportation based on the improvement of the modified thermodynamic perturbation theory. Practical value of results of the study is the improved mathematical apparatus and the results of its application which are suitable for developing a list of recommendations and organizational and technical measures for obtaining ultra-high purity gaseous hydrogen as an ecologicale safe renewable fuel in environmental protection technologies both during the times of armed aggression and during the post-war reconstruction of critical infrastructure and economic potential of our country. The main part of the research is devoted to the adaptation of the mathematical apparatus of the modified perturbation theory to describe the sorption processes of the interaction of hydrogen, which is in the state of a gas mixture, and intermetallic compounds of the type TiMn_1,5. It has been shown that based on sorption metal hydride technologies of the type TiMn_1,5 it is possible to achieve ultra-high purity of gaseous hydrogen as a commercial product when using it as an environmentally safe, renewable type of motor fuel. Mathematical modeling of hydrogen sorption by intermetallic compounds, performed on the basis of the mathematical apparatus of the thermodynamic perturbation theory improved in the study and on the example of the intermetallic hydride TiMn_1,5, based on the application of the lattice gas model for metal hydrides. A list of recommendations and organizational and technical measures has been developed for the implementation of this type of environmental protection technologies in the practice of the units of the State Emergency Service of Ukraine, in particular the operation of fire and emergency rescue equipment with internal combustion piston engines, both during armed aggression and during the post-war reconstruction of critical infrastructure and the economic potential of our country and ensuring the fulfillment of the requirements contained in the Order of the State Emergency Service of Ukraine No. 618 (on the main activity) dated September 20, 2013. «On Approval of the Regulations on the Organization of Environmental Support of the State Emergency Service of Ukraine» and in the historical perspective of achieving the sustainable development goals contained in the Decree of the President of Ukraine No. 722/2019 of September 30, 2019 «About the Goals of Sustainable Development of Ukraine for the Period up to 2030».

Abstract: This paper introduced a low-overpotential heterostructured NiCoFe-LDH@NiCo₂O₄ electrocatalyst for hydrogen evolution reaction (HER). The hecterostructure was synthesized by the hydrothermal method. The electrocatalyst was coated on a Nikel foam (NiCoFe-LDH@NCO/NF) to make the electrodes. The synergistic effects between NiCoFe-LDH and NiCo₂O₄, coupled with the unique structure and high electrochemically active surface area, resulted in high-performance HER electrocatalytic activity. The HER performance of NiCoFe-LDH@NCO/NF electrode exhibited a low overpotential of 147 mV at a current density of 50 mAcm⁻² and a Tafel slope of 83 mVdec⁻¹. The abundance and low cost of the constituent materials make NiCoFe-LDH@NCO/NF a promising candidate for practical applications in water splitting for sustainable hydrogen production.

Abstract: In this study, we tried to grow SiC ingots with high resistivity and polytype stability with adoption hydrogen mixed gas flow to the PVT method. Three different types of growth atmosphere of N₂+Ar, H/Ar ratio:10% and 30% were employed. The polytype inclusion, crystal shape and transparency, and their resistivity were systematically investigated by UVF images, exposing backlighting, and high resistivity analysis using COREMA (Contactless Resistivity Mapper), respectively. The SiC ingot grown with adoption N₂+Ar exhibited a suppression of polytype inclusion, a convex shape and a lower resistivity. In contrast, the SiC ingot with more higher H/Ar ratio of 30% than that of 10% shows no polytype inclusion and highest resistivity of 1.7E11mΩ∙cm. The growth atmosphere of relative higher H/Ar ratio in SiC crystal growth could be led the way to manufacture HPSI (high-purity semi-insulating)-SiC single crystal with polytype stability.

Abstract: Density-functional-theory calculations have been performed to investigate the magnetism induced in silicene and germanene by hydrogen terminations. We varied the H-terminated structures from monomers to pentamers. Silicene and germanene exhibit magnetic properties after H termination, as indicated by the appearance of magnetic moments. The greater the magnetic moment, the more H atoms are added in the same direction. Conversely, H atoms added in the opposite direction reduce the magnetic moment. We calculated the adsorption energy for each variation of H-terminated silicene and germanene. The results show that both have negative adsorption energies. H-terminated silicene has a more negative adsorption energy than H-terminated germanene. For example, pentamer silicene has an adsorption energy of -10.37 eV, while pentamer germanene has an adsorption energy of -7.39 eV. This indicates that H is more easily adsorbed on silicene. Thus, H-terminated silicene and germanene are suitable for magnetic material device applications.

Abstract: We have long heard the terms sustainable future and renewable energy coming from many directions. But many people think of them as challenges for the future. However, robots, self-driving cars and smart houses around us also prove that the future is only a matter of hours. With artificial intelligence developing at a rapid pace, we need to find a safe way to cover our energy hunger. Currently, we can almost find fossil fuels or electrically powered vehicles on the roads. However, non-renewable energy sources are already being replaced by renewables day by day. However, renewable energy generated by the most used weather-dependent solar and wind farms has to be stored due to uneven energy use. The solution is not only batteries, but also hydrogen produced by water splitting. The energy storage potential of hydrogen lies in its high specific energy content, zero-emissions and can be produced in almost unlimited quantities. The domestic hydrogen strategy is also related to this, which provides guidance for phasing out diesel use as part of the transition to clean modes of transport. Reducing the carbon footprint of vehicle traffic from hydrogen use and extending hydrogen mobility to bus, train and waste transport requires the deployment of new hydrogen refueling infrastructure. However, these goals, new operating conditions and their integration into new applications that are in direct contact with consumers pose security challenges. Safety is the most important element for the smooth development and acceptance by society of new technologies. Therefore, in this article we will deal with the safety risks and dangers of hydrogen refueling stations. We describe the advantages, dangers and physical chemical properties of hydrogen. We present the system elements and operating principle of a hydrogen fueling station. Finally, we list the risk reduction measures and safety approaches that promote the safe design, operation and management of hydrogen-based technologies in Hungary.

Abstract: The paper presents the results of an investigation into the reduction processes of iron ore titanomagnetite pellets using synthesis gas. The thermodynamic modelling was carried out using the TERRA software package. Synthesis gas is a mixture of carbon monoxide (CO) and hydrogen (H₂), as well as other gases such as CO₂ and N₂. It is primarily used in the production of liquid fuels and chemical products, and is produced through the initial conversion of natural gas and coal fuel. The TERRA software package was used to model and predict chemical and phase transformations in pellets during reduction. The model takes into account the influence of temperature, hydrogen concentration, and other parameters on the reduction kinetics. Calculations were carried out with different gas mixtures and conditions to evaluate the model's effectiveness. The thermodynamic model constructed corresponds to the literature and calculated data and can be used to optimize the reduction process under various production conditions.

Abstract: In this study, a single-cell, zero-gap, unipolar alkaline water electrolyzer which operates on a 30 wt.% KOH electrolyte solution was developed for production of hydrogen. Suitable material properties such as density, toughness, electrical conductivity, and corrosion resistivity were evaluated in Ansys Granta 2019 with the aid of material property charts; and thermal and stress simulations of the modelled components performed using Autodesk Inventor Nastran 2019. A DC power source supplied voltages below 3.0 V across the nickel electrodes, maintaining an operating temperature of 50 °C, and operating pressure at 0.1 MPa. The electrolytic process produced hydrogen and oxygen gases at the electrodes, and the membrane performed the gas separation. Polytetrafluoroethylene plastic was experimentally found to be a superior and more suitable material for the electrolyzer endplates and spacers to polypropylene plastic. Polypropylene nonwoven geotextile fabric was also found to be a low-cost and efficient membrane material, against Zirfon Perl UTP 500 membrane which is an efficient but expensive industrial membrane; polyester geotextile fabric got corroded after about 24 hours of good service. The optimal performance of the electrolyzer cell was obtained at a cell voltage of 2.2 V and a current of 1.30 A, while producing 14 ml of hydrogen gas per minute. This performance gave an electrolysis efficiency of 55.6%, an energy efficiency of 67.3%, and a hydrogen production efficiency of 75.4%. The produced hydrogen and oxygen gases generated electrical energy in a reversible PEM fuel cell device which powered a 0.2 W DC electric motor for a minute.